Files - Expert Oracle Database Architecture - page 73

Chapter 3
Files
In this chapter, we will examine the eight major file types that make up a database and instance. The files associated
with an instance are simply
• Parameter files : These files tell the Oracle instance where to find the control files, and they also
specify certain initialization parameters that define how big certain memory structures are,
and so on. We will investigate the two options available for storing database parameter files.
• Trace files : These are diagnostic files created by a server process, generally in response to some
exceptional error condition.
• Alert files : These are similar to trace files, but they contain information about “expected”
events, and they also alert the DBA in a single, centralized file of many database events.
The files that make up the database are
• Data files : These are for the database; they hold your tables, indexes, and all other data
segment types.
• Temp files : These are used for disk-based sorts and temporary storage.
• Control files : These tell you where the data files, temp files, and redo log files are, as well as
other relevant metadata about their state. They also contain backup information maintained
by RMAN (Recovery Manager, the backup and recovery tool).
• Redo log files : These are your transaction logs.
• Password files : These are used to authenticate users performing administrative activities over
the network. We will not discuss these files in any great detail as they are not a necessary
component of any Oracle database.
In Oracle 10 g and above, there are a couple of optional file types that are used by Oracle to facilitate faster backup
and faster recovery operations. These two files are
• Change-tracking file : This file facilitates a true incremental backup of Oracle data. It does not
have to be located in the Fast Recovery Area, but as it relates purely to database backup and
recovery, we'll discuss it in the context of that area.
• Flashback log files : These files store “before images” of database blocks in order to facilitate
the FLASHBACK DATABASE command.